Water hammer prevention valve and method

Abstract

A valve for preventing water hammer includes a speed reduction device for reducing a speed at which the valve may be closed. A method of preventing water hammer includes closing a valve at a fire hydrant after extracting water from the fire hydrant, in which the valve comprising a speed reduction device that increases an amount of time needed for closing the valve, and operating the valve to close the valve comprises operating the speed reduction device.

What is claimed is: 
     
       1. A valve for preventing water hammer, said valve comprising:
 a gate valve having a gate that is translated in and out of a channel of the valve by rotation of a valve handle; and 
 a speed reduction device for reducing a speed at which said valve may be closed, the speed reduction device comprising a gear train with a gear ratio such that a number of rotations of said valve handle results in a lesser number of rotations of a screw that translates said gate with respect to said channel; 
 wherein threads on the screw supporting the gate are reversed such that, with the gear train reversing a direction of rotation of the valve handle as applied to the screw, a clockwise rotation of the handle will close the gate and a counter-clockwise rotation of the handle will open the gate. 
 
     
     
       2. The valve of  claim 1 , further comprising a set of threads at one end of the channel sized for mating with the threads of a pumper nozzle of a fire hydrant. 
     
     
       3. The valve of  claim 2 , further comprising a set of threads at an opposite end of the channel sized for mating with a hose of a water truck. 
     
     
       4. The valve of  claim 1 , wherein the screw comprises a worm gear. 
     
     
       5. The valve of  claim 1 , wherein the gear train consists of two gears of two different sizes. 
     
     
       6. A method of preventing water hammer, the method comprising:
 closing a valve at a fire hydrant after extracting water from said fire hydrant, the valve comprising a gate valve having a gate that is translated in and out of a channel of the valve by rotation of a valve handle, and closing the valve comprising rotating the valve handle in a clockwise direction; 
 wherein the valve comprising a speed reduction device that increases an amount of time needed for closing said valve, and operating said valve to close said valve comprises operating a speed reduction device such that said increased amount of time needed for closing said valve prevents an occurrence of water hammer associated with said closing of said valve; 
 wherein the speed reduction device for reducing a speed at which said valve may be closed comprising a gear train with a gear ratio such that a number of rotations of said valve handle results in a lesser number of rotations of a screw that translates said gate with respect to said channel; 
 wherein threads on the screw supporting the gate are reversed such that, when the gear train reverses a direction of rotation of the valve handle as applied to the screw, a clockwise rotation of the handle will close the gate and a counter-clockwise rotation of the handle will open the gate. 
 
     
     
       7. The method of  claim 6 , further mating a set of threads at one end of the channel with the threads of a pumper nozzle of a fire hydrant. 
     
     
       8. The method of  claim 7 , further comprising mating a set of threads at an opposite end of the channel with a hose of a water truck. 
     
     
       9. The method of  claim 6 , wherein the screw comprises a worm gear. 
     
     
       10. The method of  claim 6 , wherein the gear train consists of two gears of two different sizes.